The intracellular free Ca 2+ concentration determines several important functions in lacrimal acinar cells including exocrine activity and exocytosis, development and differentiation, intracellular signaling and gene expression. The application's objectives are to gather preliminary data to develop a research basis for a subsequent application through the R01 mechanism and to explore the feasibility of the proposed research concept. The scientific goals are to understand the contribution of intracellular Ca 2+ channels (ICCs) to the function of lacrimal acinar cells and to identify the regulation of these proteins as potential targets for the treatment of ocular manifestations of rheumatic and skin diseases affecting lacrimal acinar cell function. The central hypothesis of the present application is that ICCs determine (a) physiological and pathophysiological processes in lacrimal acinar cells, and (b) functional properties of lacrimal acinar cells through their differential distribution and their interaction with regulatory factors. The specific aims for testing this hypothesis in mammalian lacrimal acinar cells are: 1) to determine the subcellular localization of ICCs and of their signaling partners in lacrimal acinar cells using immunocytochemistry, confocal laser scanning and electron microscopy; 2) to analyze the biophysical and pharmacological characteristics of ICCs and their regulation by the redox state in lacrimal acinar cells using single channel electrophysiology; 3) to identify and measure the contribution of oxidative stress to ICC mediated intracellular Ca 2+ signaling in lacrimal acinar cells with optical imaging of intracellular calcium concentrations. ICCs and functionally associated proteins will be localized using immunocytochemistry, confocal laser scanning and electron microscopy. The mechanisms of action and regulation of ICCs will be determined with single channel electrophysiology. The contribution of ICCs to intracellular Ca 2+ signaling in lacrimal acinar cells will be measured using imaging of intracellular Ca 2+ concentrations, and confocal laser scanning microscopy. The preliminary data that will be obtained from the specific aims will lay the groundwork for a possible pharmacological control of intracellular Ca 2+ concentration that are essential for the development of treatments of ocular manifestations of rheumatic diseases affecting lacrimal acinar cell function.